High-voltage fuse with plugs of sheet metal

ABSTRACT

A fuse for elevated circuit voltages having substantially helically wound fusible element means supported by a plurality of angularly displaced rods of electric insulating material. The casing of the fuse is closed by hollow plugs of sheet metal and the rods for supporting the fusible element means are supported by sheet metal supports affixed to the end surfaces of said hollow plugs.

United States Patent [191 Salzer Mar. 11, 1975 HIGH-VOLTAGE FUSE WITHPLUGS 01F SHEET METAL Erwin Salzer, Waban, Mass.

[75] lnventor:

[73] Assignee: The Chase-Shawmut Company,

Newburyport, Mass.

[22] Filed: Feb. 20, 1974 [21] Appl. No: 444,095

[52] US. Cl 337/161, 337/159, 337/252 [51] Int. Cl. HOlh 85/02 [58]Field of Search 337/159-162,

[56] References Cited UNITED STATES PATENTS 3,680,019 7/1972 Kozacka337/161 3,810,061 5/1974 Salzcr 337/159 Primary Examiner-J. D. MillerAssistant Examiner-lired E. Bell [57] ABSTRACT A fuse for elevatedcircuit voltages having substantially helically wound fusible elementmeans supported by a plurality of angularly displaced rods of electricinsulating material. The casing of the fuse is closed by hollow plugs ofsheet metal and the rods for supporting the fusible element means aresupported by sheet metal supports affixed to the end surfaces of saidhollow plugs.

6 Claims, 3 Drawing Figures HIGH-VOLTAGE FUSE WITH PLUGS OF SHEET METALBACKGROUND OF THE INVENTION Many fuses for elevated circuit voltagesrequire fusible element means exceeding in length the length of thecasing, or fuse tube. In such instances the fusible element means arewound substantially helically. Conventional fuses having helically woundfusible element means include a mandrel arranged in coaxial relation toand inside of the casing, or fuse tube. This mandrel is star-shaped incross-section. The fusible element means which are generally inribbon-form are wound helically around the aforementioned mandrel.Mandrels of this description ought to be made of expensive electricinsulating materials and this is one of the limitations of fuses relyingon mandrels of the above description for supporting the fusible elementsthereof. Another serious limitation of fuses relying on mandrels of theabove description for supporting the helically wound fusible elementsthereof resides in the fact that the volume of such mandrels isrelatively large, and thus limits the volume inside of a casing, or fusetube, of given size which is available for a pulverulent arcquenchingfiller such as, for instance, quartz sand. Still another limitation offuses having mandrels of the above description resides in the relativelylarge danger of tracking, or formation of more or less conductivesurface layers.

US. Pat. No. 3,680,019 to Frederick J. Kozacka, July 25, 1972 forHIGH-VOLTAGE FUSE HAVING A PLURALITY OF FUSE LINKS WOUND HELI- CALLYAROUND AN INSULATING MANDREL discloses a fuse for elevated circuitvoltages wherein the conventional mandrels of the above description arereplaced by a fuse-link-supporting mandrel structure formed of fourseparate or individual plates of electric insulating material arrangededgewise relative to the helically wound fusible elements. which theysupport. The copending patent application of Frederick J. Kozacka, filedJan. 3, I974, Ser. No. 430,477 for ELEC- TRIC FUSE FOR ELEVATED CIRCUITVOLTAGES discloses a further improvement and a simplification of thefusible element supporting means disclosed in the above referred-topatent.

The present invention is based upon the structures disclosed in theabove referred-to patent application and patent. Its principal object isto drastically reduce the amount of metal required for fuse structuresof the kind disclosed in the above referred-to patent, and in the abovereferred-to patent application, in view of the current severe shortageof metals, in particular copper and copper alloys.

SUMMARY OF THE INVENTION Fuses embodying this invention include atubular easing of electric insulating material and a substantiallyhelically wound fusible element means in ribbon form arranged inside andin coaxial relation to said casing. A pulverulent arc-quenching fillerinside said casing embeds said fusible element means. Said fusibleelement means is or are supported by a plurality of separate angularlydisplaced rods of electric insulating material arranged parallel to theaxis of said casing. The casing is closed by a pair of hollow plugs ofsheet metal having end surfaces and having lateral surfaces engaging theinner surface of said casing and being provided with asealing-medium-containing groove means. A plurality of sheet metalsupports for said plurality of rods is affixed to said end surfaces ofsaid pair of hollow plugs and engaged by the ends of said plurality ofrods.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front elevation of asub-assembly used in manufacturing a fuse embodying this invention. someportions of the sub-assembly being broken away to reduce the length ofits pictorial representation;

FIG. 2 is in part a front view and mainly a longitudinal section alongIIII of FIG. 3 ofa complete fuse embodying this invention, some of theportions of the fuse being broken away to reduce the length of itspictorial representation; and

FIG. 3 is a cross-section of the structure of FIG. 2 substantially alongIII-III of FIG. 2.

DESCRIPTION OF PREFERRED EMBODIMENT To manufacture a fuse embodying thisinvention involves making a sub-assembly as shown in FIG. 1. Thesub-assembly is formed by a pair of hollow plugs I of sheet metal. Plugs1 have end surfaces and lateral sur faces provided with a pair ofcircumferential grooves or groove means 2. Reference numeral 4 has beenapplied to indicate rods of electric insulating material, e.g. glassmelamine, forming spacers for hollow plugs l and supports for one ormore fusible elements 5 which are wound substantially helically aroundrods 4. FIG. I shows a structure including one single fusible element 5of which but the ends immediately adjacent hollow plugs 1 have beenshown, i.e., the intermediate portions of the fusible element 5 havebeen deleted in FIG. I (and the same also applies as to FIG. 2). Rods 4are subjected to a radially inwardly directed bending action when ribbonfuse link 5 is helically wound around rods 4. To minimize bending ofrods 4 their width in radial direction exceeds their thickness at rightangles to said direction. To further minimize bending of rods 4 the sameare also provided with one or more annular braces 8 between the endsthereof. Annular brace 8 is provided with four radial slots angularlydisplaced and the radially inner edges of rods 4 are coextensive withthe closed ends of the slots in annular brace or braces 8. A pluralityof sheet metal supports 3 for rods 4 is affixed to the end surfaces ofhollow sheet metal plugs l and engaged by the ends of rods 4. Each ofsheet metal supports 3 is preferably formed by a flanged tubular elementaffixed with the flanged axially outer end thereof to one of the endsurfaces of hollow sheet metal plugs l. The axially inner ends offlanged tubular elements are engaged by link-supporting spacing rods 4.The axially inner ends of flanged tubular elements 3 are preferablysquashed around the ends of rods 4. The squashing operation may beeffected before affixing flanged tubular elements 3 to hollow plugs l.The flanged tubular elements 3 may be affixed to hollow plugs l byspot-welds along the flanges of elements 3. In the drawings the axiallyinner ends of parts 3 have a smaller diameter than the axially outerends thereof, but this is not a necessary feature of the structure underconsideration. Nor is it a necessary feature of the structure underconsideration to squash the ends of the tubular elements 3 into whichrods 4 project. Rods 4 may be simply press-titted into tubular elements3 and firmly positoned therein by a seal of an epoxy resin fully closingthe axially inner ends of tubular elements 3. The ends of fusibleelement 5 are affixed to, and conductively connected to, tubularelements 3, e.g. by spot-welds.

After completion of the sub-assembly shown in FIG. 1 the latter isinserted into a tubular casing 6 of insulating material, e.g. melamineglass cloth and pinned to the latter. Preparatory to such insertionannular grooves 2 in hollow plugs l are filled with a sealing compound,preferably silicone rubber. Reference numerals 7 have been applied toindicate pins projecting transversely through casing 6, the lateralsides of hollow sheet metal plugs l and the portions of tubular elements3 adjacent the end surfaces of plugs 1. Pins 7 are arranged at levelssituated between grooves 2 in plugs l and project into the non-squashedportions of tubular elements 3. The final process step in manufacturingthe fuse shown in FIGS. 2 and 3 consists in filling the pulverulentarc-quenching filler 9 into casing 6 by a filling aperture (not shown)in one of plugs 1 which is sealed upon completion of the fillingoperation.

For the purpose of better illustrating the structure under considerationFIG. 1 shows bores in hollow plugs l and in tubular elements 3 intendedto receive the pins 7. These bores are actually drilled only uponinsertion of parts 1,3,4 and 5 into casing 6 in one and the samedrilling operation by which the registering pinreceiving bores in casingl are drilled.

I claim as my invention:

1. An electric fuse including a. a tubular casing of electric insulatingmaterial;

b. substantially helically wound fusible element means in ribbon formarranged inside of and in coaxial relation to said casing;

c. a pulverulent arc-quenching filler inside said casing embedding saidfusible element means;

d. a plurality of separate angularly displaced rods of electricinsulating material arranged parallel to the axis of said casingsupporting said fusible element means;

e. a pair of hollow plugs of sheet metal closing the ends of saidcasing, said pair of plugs having end surfaces and having lateralsurfaces, engaging the inner surface of said casing and being providedwith a sealing-medium-containing groove means; and

f. a plurality of sheet metal supports for said plurality of rodsaffixed to said end surfaces of said pair of hollow plugs and engaged bythe ends of said plurality of rods. I

2. An electric fuse as specified in claim 1 including pins projectingthrough said casing and through said lateral surface of one of said pairof hollow plugs into one of said plurality of sheet metal supports forsaid plurality of rods.

3. An electric fuse as specified in claim 1 wherein each of said lateralsurfaces of said pair of hollow plugs is provided with a pair of groovesand wherein said casing is affixed to said pair of hollow plugs by pinsarranged between said pair of grooves and having radially inner endsprojecting into one of said plurality of sheet metal supports for saidplurality of rods.

4. An electric fuse as specified in claim 1 wherein each of the ends ofsaid fusible element means is affixed to and conductively connected withone of said plurality of sheet metal supports for said plurality ofrods.

5. An electric fuse as specified in claim 1 wherein said plurality ofsheet metal supports for said plurality of rods is formed by a pluralityof flanged tubular elements affixed with the flanged axially outer endsthereof to said end surfaces of said hollow plugs and being engaged atthe axially inner ends thereof by said plurality of rods.

6. An electric fuse as specified in claim 5 wherein the axially innerends of said plurality of flanged tubular elements are squashed, andwherein said casing is affixed to said hollow plugs by radiallyextending pins having radially inner ends projecting into the axiallyouter non-squashed portions of said flanged tubular ele-

1. An electric fuse including a. a tubular casing of electric insulatingmaterial; b. substantially helically wound fusible element means inribbon form arranged inside of and in coaxial relation to said casing;c. a pulverulent arc-quenching filler inside said casing embedding saidfusible element means; d. a plurality of separate angularly displacedrods of electric insulating material arranged parallel to the axis ofsaid casing supporting said fusible element means; e. a pair of hollowplugs of sheet metal closing the ends of said casing, said pair of plugshaving end surfaces and having lateral surfaces engaging the innersurface of said casing and being provided with asealing-medium-containing groove means; and f. a plurality of sheetmetal supports for said plurality of rods affixed to said end surfacesof said pair of hollow plugs and engaged by the ends of said pluralityof rods.
 1. An electric fuse including a. a tubular casing of electricinsulating material; b. substantially helically wound fusible elementmeans in ribbon form arranged inside of and in coaxial relation to saidcasing; c. a pulverulent arc-quenching filler inside said casingembedding said fusible element means; d. a plurality of separateangularly displaced rods of electric insulating material arrangedparallel to the axis of said casing supporting said fusible elementmeans; e. a pair of hollow plugs of sheet metal closing the ends of saidcasing, said pair of plugs having end surfaces and having lateralsurfaces engaging the inner surface of said casing and being providedwith a sealing-medium-containing groove means; and f. a plurality ofsheet metal supports for said plurality of rods affixed to said endsurfaces of said pair of hollow plugs and engaged by the ends of saidplurality of rods.
 2. An electric fuse as specified in claim 1 includingpins projecting through said casing and through said lateral surface ofone of said pair of hollow plugs into one of said plurality of sheetmetal supports for said plurality of rods.
 3. An electric fuse asspecified in claim 1 wherein each of said lateral surfaces of said pairof hollow plugs is provided with a pair of grooves and wherein saidcasing is affixed to said pair of hollow plugs by pins arranged betweensaid pair of grooves and having radially inner ends projecting into oneof said plurality of sheet metal supports for said plurality of rods. 4.An electric fuse as specified in claim 1 wherein each of the ends ofsaid fusible element means is affixed to and conductively connected withone of said plurality of sheet metal supports for said plurality ofrods.
 5. An electric fuse as specified in claim 1 wherein said pluralityof sheet metal supports for said plurality of rods is formed by aplurality of flanged tubular elements affixed with the flanged axiallyouter ends thereof to said end surfaces of said hollow plugs and beingengaged at the axially inner ends thereof by said plurality of rods.